The present invention relates to integrated circuit modules and, more particularly to integrated circuit modules suitable for supporting arrays of infrared detector elements in a space environment.
Infrared detector modules are used for a variety of purposes including space surveillance. In view of the stringent environmental and performance demands of such systems, as well as space limitations relating to launch and orbit, substantial needs have developed to miniaturize the modules while retaining high performance and high reliability of operation.
For example, in order to provide accurate resolution of infrared imaging it may be necessary to space infrared detector elements by 4 mils or less. It is also desirable to provide some form of focal plane processing in order to limit the need to communicate raw data to remote processors. Consequently, there has developed a need to provide an improved module structure which not only satisfies the dense connectivity problems but also permits on-focal plane processing of the raw input signals.
A variety of contructions have been proposed for integrated circuit modules. One such structure is disclosed in U.S. Pat. No. 4,703,170 issued to Charles E. Schmitz and assigned to the common assignee. One area of difficulty with respect to such modules concerns the physical means for connecting the infrared detector array, bonded to a buffer or contact board or interface device to the module supporting the processing circuitry. Common techniques for such effecting such physical and electrical connections include the formation of indium bumps on the surface of the detector interface device which abut against conductive regions formed on vertical edge surfaces of the module layers. The indium bumps of the interface device and the edge surfaces of the module are typically held in place by an insulating adhesive material. In such a structure the individual layers are not supported by the structure of the detector interface device or by the shape or structure of the module layers. Such a construction has several drawbacks. It not only requires tedious alignment of the detector interface device and the module, but it also requires that the entire detector interface device/module interface be encased in adhesive as a means to connect the module to the detector interface device. Thus, individual module layers cannot be selectively removed from the module. The fabrication of such a module typically proceeds by forming a rigid multilayer module first before connecting the module to the detector interface device.
As a practical matter, there is the difficulty of spacing the layers to match the spacing of the detector elements, which is the same as that of the interface device or contact board, and to make readily electrical contact between the stacked layers and the contact board. Further, the extreme thinness of the module layers and the dense processing requirements result in a predictable number of defects which frequently cannot be identified until the module layers are connected to the detector interface device. However, because the module layers are permanently connected, defects with respect to any particular layer typically result in discarding the entire module.
Accordingly, there exists a need for developing an alternate arrangement for connecting module layers with the detector interface device that renders the physical and electrical connections more reliable, less tedious, and facilitates selective replacement of individual layers even after the module is formed and connected to the detector interface device.